Observation of wave packets with simultaneous electronic, vibrational, and rotational degrees of freedom in Li2

Using ultrafast pump-probe spectroscopy, we observe quantum beats between rovibrational states located on the uncoupled bound G1Πg+ and F1Σg+ electronic curves of Li2. From a pure launch state (A1Σu+vA,JA=11,28), a wave packet is prepared using the output from a visible ultrafast optical parametric amplifier and is photoionized by an 800 nm ultrafast pulse. As the OPA wavelength is scanned, a vibrational progression of rotational quantum beats on the G curve is observed. At energies around 35 000 cm−1, in addition to rotational beats on the G curve, vibrational, rotational, and electronic beating between the G and F curves is observed.